Development of a medium power L-band traveling-wave amplifier

The development and performance of a high gain medium power traveling wave amplifier are described. Powers up to 7 watts at 15% efficiency have been achieved. The small signal gain approaches 50 db in the middle of the band, and exceeds 35 db over a 2 to 1 range of frequencies. The tube itself consists of a glass supported helix with a metal shell at one end, housing the cathode structure, and a copper collector at the other end. The input and output couplings are made by means of coupled helices which are mounted in a brass tube or matching structure which is external to the vacuum envelope. The matching structure is supported in the focussing solenoid. The effect of shield diameter, glass thickness and beam perveance on bandwidth are discussed. Other features of particular interest are the attenuator and coupling designs.